Using Estrogenic Activity and Nontargeted Chemical Analysis to Identify Contaminants in Sewage Sludge

Abstract

Diverse organic compounds, many derived from consumer products, are found in sewage sludge worldwide. Understanding which of these poses the most significant environmental threat following land application can be investigated through a variety of predictive and cell-based toxicological techniques. Nontargeted analysis using high-resolution mass spectrometry with predictive estrogenic activity modeling was performed on sewage sludge samples from 12 wastewater treatment plants in California. Diisobutyl phthalate and dextrorphan were predicted to exhibit estrogenic activity and identified in >75% of sludge samples, signifying their universal presence and persistence. Additionally, the application of an estrogen-responsive cell bioassay revealed reductions in agonistic activity during mesophilic and thermophilic treatment but significant increases in antagonism during thermophilic treatment, which warrants further research. Ten nontarget features were identified (metoprolol, fenofibric acid, erythrohydrobupropion, oleic acid, mestranol, 4'-chlorobiphenyl-2,3-diol, medrysone, scillarenin, sudan I, and N,O-didesmethyltramadol) in treatment set samples and are considered to have influenced the in vitro estrogenic activity observed. The combination of predictive and in vitro estrogenicity with nontargeted analysis has led to confirmation of 12 estrogen-active contaminants in California sewage sludge and has highlighted the importance of evaluating both agonistic and antagonistic responses when evaluating the bioactivity of complex samples.

Figure 1

(a) demethylation pathway of dextromethorphan, the primary ingredient found in all cough medicines, via the liver metabolic CYP2D6 pathway into dextrorphan, an optical isomer of levorphanol (b).

Figure 2

ER-CALUX activity measured in estradiol equivalents Agonist activity is percent activity relative to 1 nM E2 treatment. Antagonist activity is the observed suppression of 1nM E2 (calculated 1 – observed activity of extract where 1nM E2 was added).